Observers believe his limited choice of neckwear might be an attempt to subliminally push his green credentials - and it's surely no coincidence that his party's much derided new 'squiggle' logo is in a very similar shade.

But is it really the same tie or does Mr Cameron keep 15 identical designs to hand in a special cabinet, like Batman and his Batsuits?

In fact, The Mail on Sunday has discovered that Mr Cameron has two very similar lime ties.

His favourite, which he wore the day he was elected on December 6 last year, is an £85 design from Timothy Everest, an international tailor based in London's Spitalfields who has also dressed David Beckham and Tom Cruise.

The substitute is a £49 tie with subtle silver spots by Jermyn Street tailors Thomas Pink, known as a Romeo Spot and made from French silk.

Claudia Ottobrino, spokeswoman for Timothy Everest, said: "Mr Cameron came to see us in the build-up to his leadership campaign and asked our advice on what he should wear.

"He had a consultation with one of our tailors for a whole outfit. His brief was that he wanted something fairly neutral and media-friendly. We suggested the green tie."